Known in the art is an acoustic wave device which has an element substrate, an excitation electrode which is located on the element substrate, a resinous cover which covers the excitation electrode, and solder bumps which are electrically connected to the excitation electrode and are provided on an top surface or the like of the cover. Such an acoustic wave device is mounted on a mounting board by being arranged with an top surface of the cover made to face a mounting surface of the mounting board, making the solder bumps abut against pads which are arranged on the mounting surface of the mounting board, and heating in that state. Further, the mounted acoustic wave device is covered by a mold resin to be sealed.
In Patent Literature 1, the cover of the acoustic wave device is formed with openings which penetrate from the bottom surface (the surface on the element substrate side) to the top surface. The openings are filled entirely with solder. The filled solder is melted once and resolidified before mounting of the acoustic wave device on the mounting board, whereby the portions at the cover top surface side are rounded by surface tension and form spherical bumps. The bumps are separated from the inner circumferential surfaces of the openings in the process of forming the spherical shapes and stick out from the top surface of the cover. However, when the bumps are heated and the acoustic wave device is mounted on the mounting board, the bumps return from the spherical shapes to the shapes filled in the openings and the top surface of the cover contacts the mounting surface of the mounting board. As a result, in Patent Literature 1, it is considered that the lid body becomes resistant to pressure of the mold resin, and the bumps are surrounded by the cover, so the reliability becomes higher.
In Patent Literature 2, the cover of the acoustic wave device is formed with openings which penetrate from the bottom surface to the top surface. The openings are filled with metal up to positions somewhat lower than the top surface of the cover, whereby columnar terminals are formed. Solder bumps are formed on the terminals and bury the upper ends of the openings.
In Patent Literatures 1 and 2, the solder bumps are filled in the openings of the cover at the stage where at least the acoustic wave device is mounted on the mounting board. Accordingly, the solder bumps change to the shapes of the openings of the cover. As a result, for example, the solder bumps are formed to shapes where stress easily concentrates at positions which contact edge portions which are formed by the inner circumferential surfaces of the openings and the top surface of the cover and the solder bumps easily crack. That is, the degree of freedom in the shapes of the bumps is restricted by the shapes of the openings of the cover, therefore various inconveniences arise.
Accordingly, it is desired to provide an acoustic wave device which is capable of improving the degree of freedom in the shapes of the bumps and an electronic component which has the acoustic wave device.